What happens if a condenser rated for a safe working voltage of 250 volts DC is used across a 250 volt 60 cycle AC line?

Using a condenser that is rated for a safe working voltage of 250 volts DC across a 250-volt 60-cycle AC line poses a significant risk of failure because the voltage rating for DC and AC is not directly interchangeable. Capacitors are typically rated for their maximum DC voltage, which differs from the AC voltage rating due to the alternating nature of AC current.

When connected to an AC source, the effective or RMS voltage of 250 volts AC is approximately 353 volts peak (calculated using the formula V_peak = V_RMS × √2), which exceeds the DC rating of the capacitor. This exceedance of the voltage limit can cause the dielectric material within the capacitor to break down, leading to a failure. This breakdown may manifest as a short circuit or, in extreme cases, result in catastrophic failure of the capacitor.

Given these conditions, the most accurate outcome of using this condenser inappropriately is that it may break down. This highlights the importance of ensuring that capacitors are properly rated for the type of voltage they will encounter in a circuit.